THE EAR-TRUMPET. 521 



On the left hand of the illustration is shown the wonderful 

 apparatus by means of which the Swan produces its far- 

 resounding cry. The windpipe, or "trachea/' as it is 

 technically named, passes down the neck, protected by the 

 bones, until it reaches the chest. There it leaves them, enters 

 the cavity of the chest, and contorts itself in such a manner as 

 to obtain greater length, just as is the case with the trombone 

 and valved instruments. 



Acoustics as Aids to Surgery. 



We have already seen how the air- vibrations poured in at 

 the small end of the trumpet can make resonant notes. "We 

 have now to see how the reverse process can be employed, and 

 sounds poured into the larger end be conveyed to the ear. 



The Ear-trumpet is a familiar example of such an instru- 

 ment, and, as it is shown in the illustration, there is no need 



EAR-TRUMPET. CONCHA OF HUMAN EAR. 



of further description. It is rather remarkable, by the way, 

 that the length of tube does not seem to interfere with the 

 conveyance of sound, as may be seen by the speaking-tubes 

 which are now so common in private houses, hotels, and 

 offices. 



I know of one church in which there is a special seat for 

 deaf persons. The reading-desk and pulpit are both fitted 

 with the large ends of Ear-trumpets. From them pass tubes 

 under the flooring, and so into the seat, where they can be 

 applied to the ear of the deaf worshippers. 



On the right hand is the " Concha," as it is called, of the 

 human ear, which is evidently constructed for the purpose of 

 collecting and concentrating sounds. Instinctively, if we wish 



